Loop detector apparatuses are commonly used in roadways and other ground surfaces on which a vehicle travels. Generally speaking, these loop detector apparatuses include an inductive loop, a detecting mechanism, and a cable coupling the inductive loop to the detecting mechanism. The detecting mechanism provides the inductive loop with power, which creates a magnetic field in the inductive loop area having a frequency that is monitored by the detecting mechanism. When a vehicle or other metallic object passes over the inductive loop, the frequency increases. The detecting mechanism senses this increase in frequency and causes a device to perform an action.
These apparatuses may be used for a variety of different purposes, for example when detecting the presence of a vehicle waiting at a traffic light. Upon the inductive loop detecting the presence of the vehicle, the inductive loop may then transmit a signal to a device which causes the traffic light to change, thus allowing the vehicle to resume travel. In other systems, loop detector apparatuses may be employed in commercial settings to allow access to a warehouse or dock service door.
Many of these systems require the inductive loop to be buried a sufficient depth under the ground surface. As a result, installation of these apparatuses may be costly due to the below-ground placement of the loop. Further, improper installations may create difficulties in accurately sensing the presence of a vehicle. Even assuming proper installation of these apparatuses does occur, due to varying vehicle sizes, the apparatus may be unable to accurately measure a change in frequency. For example, one type of vehicle (such as a sports car) may have a low center of gravity with sufficient amounts of metal at a distance that is close enough to the inductive loop to accurately sense a change in frequency when the vehicle rolls over the inductive loop. Other types of vehicles (such as a sport utility vehicle or a delivery truck, to name a few examples) may have a higher center of gravity with a lesser amount of metal located at a distance necessary to obtain an increase in frequency. As a result, the detecting mechanism may not detect the presence of these vehicles. Other vehicle characteristics may also lead to the failure to accurately detect the vehicle.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.